1. Field of the Invention
The invention is directed to a process and a system for removing scale from the surface of high-grade steel strips in an electrolytic strip treatment installation with a plurality of electrodes which are arranged directly one after the other and connected in an alternating manner as anodic with cathodic strip polarization and as cathodic with anodic strip polarization.
2. Discussion of the Prior Art
When producing pickled hot strip or when producing cold strip with a high-quality steel, the scale which occurs must be removed from the surface of the strip. Three different types of scale may be distinguished:
1. scale formed during the production of hot strip; PA1 2. scale formed during annealing of hot strip; and PA1 3. scale formed during annealing of cold strip.
The different formation of the scale layers has been described numerous times in the literature and is familiar to those skilled in the art. The differences in scale formation have led to descaling ideas in which great compromises had to be made with respect to the quality of material, especially with respect to scale occurring in the production of hot strip and the mill scale occurring during the annealing of hot strip. Further, these concepts can be realized only at very high investment costs and also have environmental problems.
In the past, scale layers of the kind described above were commonly removed abrasively with blasting devices or by means of chemical pickling treatments. It has also been suggested to combine these two methods.
The known processes have various disadvantages. The abrasive removal of the scale by means of blasting devices, for instance, causes an unwanted increase in the roughness of the material surface from 1-1.5 nm GA to 4-6 nm RA. At the same time, blasting treatment leads to considerable loading of the environment with dust.
Treatment of strip surfaces by means of chemical pickling results in substantial environmental loading due to the acids used (HF, HNO.sub.3, H.sub.2, SO.sub.4) and the subsequent introduction of fluorine, nitrate and sulfate into the flow.